Tanning agents and a process of preparing them



i atented july 15, 1952 TANNING AGENTS AND A PROCESS OF PREPARING THEM Christoph Nikolaus Jakobus Thomsen, deceased,

late of Frankfort-on-the-Main,

Germany, by

Gertrud Thomsen, administratrix, Kelkheim- Munster in Taunus, Germany, assignor to Farbwerke Hoechst'vormals Meister Lucius & Bruning, Frankfort-on -the-Main-Hochst, Germany,

a manufacturing an d trading organization under' the laws oiLthe Allied Control Council and Allied HighCommission of Germany No Drawing. Application May 13, 1949, Serial No. 93,194. In Germany October 1, 1948 The present invention relates to tanning agents and to a process of preparing them.

The production of tanning agents from colophony is attended by considerable difficulties. In the method of direct sulfonation considerable decomposition occurs owing to the high temperatures and large excess of sulfonating agent required. Tanning agents so obtained produce dark and fiat leather.

By the addition of phenols before or during the sulfonation tanning agents can be obtained having a better fulling effect and a lighter and clearer tint, but their resistance to salts and the compatibility with extracts is generally insufficient. It is necessary for the production of serviceable tanning agents to reduce their content of electrolytes, which may be carried out by washing with water or salt liquors.

It is an object of this invention to prepare new and valuable tanning agents which are free from the drawbacks connected withthe known tanning agents prepared with the aid of colophony.

It has now been found that condensation products having a tanning action and very good properties are obtainable by sulfonating a mixture of colophony and a naphthol, reacting a phenol with the product thus obtained and then reacting the resulting condensation product with formaldehyde. Brown tanning agents are obtained which strike through rapidly and show on analysis a content of tanning matter of 90 per cent and more calculated on the total dry substance present. They maintain their good tanning action even at high pH values. In many cases they produce a well-plumped leather of an excellent rendement and great firmness, which is similar to barktanned leather.

Since it is possible in the preparation of the naphthol sulfonic acid to work with slight excess of the sulfonating agent, there is no need to eliminate any excess of electrolyte such as would otherwise be necessary in case of colophony tanning agents.

For the sulfonation together with colophony alpha-naphthol as well as beta-naphthol are suitable. The sulfonation does not involve any particular difficulties, it is carried out at elevated temperatures in the manner usual for such sulfonations. To be sure that the sulfonation occurs satisfactorily and that, before all, a sulfo-group also enters the molecule of the colophony, the sulfonation mixture is suitably heated for some time to temperatures of at least 110 C. It is of advantage to keep the temperature at the beginning of the operation somewhat lower, e. g. ap-

5 Claims. (Cl. 26025) proximately between and 100 C. The sulfonating agent may be added to the mixture of naphthol and colophony. It is also possible to introduce naphthol and/or colophony into the sulfonating agent. The introduction of colophony should be regulated so as to avoid frothing over.

The usual sulfonation agents maybe used, for in.- stance sulfuric acid of to per cent strength,

fuming sulphuric acid or chlorosulfonic acid: The relative proportions of colophony and. naphthol may be varied within Wide limits, e. g. for

each part of colophony from 1.3 up to 6 parts of naphthol. The proportion of 1 part of colophony to 2 parts of naphthol is of advantage. During the reaction predominantly moncsulfonic acids of the colophony as well as of the naphthol are formed. formed to a small extent.

The next step of the process is of the naphthol-colophony-sulfonic acids with a phenol or a mixture of phenols. As phenols may be used for example phenol itself, cresols, furthermore mixtures of .cresols or of cresols with a phenol, finally commercial products containing mixtures of mononuclear phenols, such as the so-called phenol oil containing phenol itself, cresols, xylenols and phenols with two phenolic hydroxyl groups.

The condensation of the phenol or the phenols with the sulfonie acids occurs without difiiculties and is generally terminated after about /2 hour. The reaction is terminated when the reaction product readily dissolves in water. In this case, too, the proportions between sulfonic acids and phenol may be varied within wide limits. However, it proved to be of advantage to apply about 1 part of the phenol or the phenols for about 1 part of the originally used naphthol.

The last step of the process comprises the aftertreatment of the condensation products with formaldehyde, which is advantageously performed after dilution of the condensation product by means of water. It takes place at temperatures of about 90-l00 C. The amountsof formaldehyde may vary within wide limits. It is recommended to use approximately 0.75 up to 0.95 mol of formaldehyde for each mol of phenol. Instead of free formaldehyde, compounds may be used yielding formaldehyde under the reaction conditions, for instance hexamethylene tetramine which latter compound has the advantage of liberating ammonia at the same time so as to neutralize the tanning agent.

The new tanning agents formed in the process described above are neutralized in the usual way Naphthol-disulfonic acids 1 are also:

the I reaction with organic acids and adjustedlto the desiredacidity. They are applied in the form of aqueous solutions (of about 50-60 per cent strength) as obtained according to this process.

The following examples serve'to illustrate the invention, but they are not intended to limit it thereto, the parts being by weight: 7 g

1. To 700-parts of sulfuric acid of 100 per cent strength 720 parts of beta-naphthol and 120 parts of colophony areadded at a temperature of 90-100 C., and then themixture is heated and maintained for 1% hours-at 125? C. andthen cooled to 90 C. At this temperature 400 parts of phenol and 400 parts of crudecresol and then 600 parts of water are added. After heating the aeoacie;

formaldehyde to 'act at temperatures of about 90-100 C. upon the condensation product thus mixture ofcolophony and a naphthol at elemixture to 95 C'., 675 parts of, formaldehyde solution of 30 per cent strength and 600 parts i of water are slowly introduced, while stirring well. The tanning agent is neutralized; by the addition'of 530 parts of an ammonia solution of 23 per cent strength, and adjusted with acetic acidto a suitable degree .of acidity.v The tanning agent tans through well, yields a brown full leather of good firmness and solidity, and is well suited for the production of sole-leather.

2. The procedure is the same as that described in mample .1, except that 250 parts of colophony are used. It is of advantage in this case to make two additions of 800 parts, instead of 600 parts, of water. The tanning. agenti so obtained produces even firmer leather than does the tanning agent ofExample 1.

3. The procedure is the same as that described in Example 1, except that 800 parts of crude phenol oil are used, instead of 400 parts of phenol and 400parts of crude cresol. The'properties of the tanning. agent so obtained aresimilar to those of the product of Example 1.

What isclaimed is: r

1. The products obtained. by sulfonating a mixture of colophony and anaphthol at. ele-.

vated temperatures, heat" reacting. a. phenol with the product. thus obtained and then causing vated temperatures, heat reacting a phenol with the product thus obtained and then causing formaldehyde to act at temperatures of about 90100' C. upon the condensation product thus obtained. a

4. The process which comprises sulfonating a mixture of colophony and a naphthol atelevated temperatures, heat reacting a mixture of phenols with the product thus obtained and then causing formaldehyde to act at temperatures of about 90-100 C. upon the product thus obtained; 5. The process which comprises sulfonatinga.

' mixture of colophony. and beta-naphthol at elevated temperatures, heat reacting 'a mixture of phenols with the product thus obtained and then causing formaldehyde to act at'temperatures of about 90-100 C. upon the product thus obtained.

GERTRUD' THO'MSEN, Administratria: of the Estate of Christoph Nz'lcolausxJakobus Thomsen, Deceased.

Name Date Number v Koch et al Sept. 5,1939 

1. THE PRODUCTS OBTAINED BY SULFONATING A MIXTURE OF COLOPHONY AND A NAPHTHOL AT ELEVATED TEMPERATURES, HEAT REACTING A PHENOL WITH THE PRODUCT THUS OBTAINED AND THEN CAUSING FORMALDEHYDE TO ACT AT TEMPERATURES OF ABOUT 90-100* C. UPON THE CONDENSATION PRODUCT THUS OBTAINED, SAID PRODUCTS SHOWING GOOD TANNING PROPERTIES EVEN AT HIGH PH VALUES. 